Thunderstorm over the Arctic Ocean

August 11th, 2019 |

NOAK49 PAFG 110400 CCA
PNSAFG
AKZ222-111600-

Public Information Statement…CORRECTED
National Weather Service Fairbanks AK
800 PM AKDT Sat Aug 10 2019

…Lightning Detected within 300 Miles of North Pole Today…

A number of lightning strikes were recorded between 4pm and 6pm
today within 300 miles of the North Pole. The lightning strikes
occurred near 85 degrees north, 120 degrees east, which is about
700 miles north of the Lena River Delta of Siberia. This lightning
was detected by the GLD lightning detection network which is used
by the National Weather Service. This is one of the furthest
north lightning strikes in Alaska Forecaster memory.

$$

JB

As noted by the NWS Fairbanks forecast office, lightning was detected with a thunderstorm located over the Arctic Ocean north of Siberia between 6-8 pm AKDT on 10 August (or 00-02 UTC on 11 August 2019). A sequence of AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images from NOAA-15 (at 2315 UTC), NOAA-19 (at 0100 UTC) and NOAA-15 (at 0232 UTC) (below) showed the eastward motion of this thunderstorm, which had developed in advance of a 500 hPa lobe of vorticity — the coldest cloud-top infrared brightness temperature associated with this feature was -49.9ºC (yellow enhancement) at 0100 UTC.

NOAA-19 AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images [click to enlarge]

AVHRR Visible (0.63 µm) and Infrared Window (10.8 µm) images from NOAA-15 (at 2315 UTC), NOAA-19 (at 0100 UTC) and NOAA-15 (at 0232 UTC) [click to enlarge]



Anomalous cutoff low over the Beaufort Sea

June 12th, 2019 |

GOES-17 Mid-leve Water Vapor (6.9 µm, top) and GOES-15 Water Vapor (6.5 µm. bottom) imagess [click to play animation | MP4]

GOES-17 Mid-level Water Vapor (6.9 µm, top) and GOES-15 Water Vapor (6.5 µm. bottom) images [click to play animation | MP4]

A comparison of Water Vapor images from GOES-17 (GOES-West) and GOES-15 Water Vapor images (above) showed the signature of an anomalously-deep closed low that was moving southeastward over the Beaufort Sea north of Alaska during the 11 June – 12 June 2019 period. The images are shown in the native projection of each satellite — GOES-17 is positioned over the Equator at 137.2º W longitude, while GOES-15 is located at 128º W. The improved GOES-17 spatial resolution (2 km at nadir, vs 4 km for GOES-15) and more frequent imaging (every 10 minutes, vs every 30 minutes for GOES-15) allowed for a better depiction of this cutoff low — including smaller-scale features near the center of the broad circulation.

GFS model 500 hPa geopotential height, wind, and standardized height anomaly (source) analyses at 6- hour intervals (below) indicated 500 hPa geopotential height anomaly values reached -3 to -4 sigma (lighter shade of violet) for this cutoff low.

6-hourly GFS 500 hPa geopotential height, wind, and standardized height anomaly [click to enlarge]

6-hourly GFS 500 hPa geopotential height, wind, and standardized height anomaly [click to enlarge]

Mesoscale disturbance over northern Alaska

April 17th, 2019 |

GOES-17

GOES-17 “Red” Visible (0.64 µm) and Low-level Water Vapor (7.3 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm) and Low-level Water Vapor (7.3 µm) images (above) showed a mesoscale disturbance that was moving northward over the eastern Brooks Range in far northeastern Alaska on 17 April 2019. The curved configuration of the associated cloud structure suggested that a closed circulation center was present (or had just recently developed) — while surface analyses showed an area of low pressure much farther to the south along the Alaska/Yukon border, there were no features moving northward across the region shown in the GOES-17 imagery.

Light to moderate snow was reported at Arctic Village as this mesoscale disturbance moved over the area (below).

Time series of surface weather observation data from Arctic Village [click to enlarge]

Time series of surface weather observations from Arctic Village [click to enlarge]

375-meter resolution Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images at 2131 and 2313 UTC (below) provided a more detailed view of this feature, in which the clouds exhibited an appearance suggestive of embedded convection. Cloud-top infrared brightness temperatures were as cold as -50ºC just southwest of Arctic Village on the 2313 UTC image — this corresponded to an altitude of 8.5 km on the 00 UTC Fairbanks rawinsonde data.

Suomi NPP VIIRS Day/Night Band (0.7 µm) images at 2131 and 2313 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) images at 2131 and 2313 UTC [click to enlarge]

Suomi NPP VIIRS Infrared Window (11.45 µm) images at 2131 and 2313 UTC [click to enlarge]

Suomi NPP VIIRS Infrared Window (11.45 µm) images at 2131 and 2313 UTC [click to enlarge]

13-km NAM model fields (below) showed no clear signature of either a closed circulation or a discrete vorticity center — so satellite imagery was depicting the presence of an important feature that was not captured by numerical models. While the 18 UTC model run did show an area of light precipitation moving northward toward the region, the 00 UTC model run scaled back the areal coverage of this precipitation.

3-km NAM 500 hPa height, wind and absolute vorticity [click to enlarge]

3-km NAM 500 hPa height, wind and absolute vorticity [click to enlarge]

3-km NAM Mean Sea Level Pressure and 1-hour accumulated precipitation [click to enlarge]

3-km NAM Mean Sea Level Pressure and 1-hour accumulated precipitation [click to enlarge]

Large ice lead near Utqiagvik (Barrow), Alaska

March 28th, 2019 |

Landsat-8 False Color RGB image at 2222 UTC [click to enlarge]

Landsat-8 False Color RGB images on 21 March and 28 March [click to enlarge]

A toggle between 30-meter resolution Landsat-8 False Color Red-Green-Blue (RGB) images viewed using RealEarth (above) revealed a large ice lead that had opened up to the east of Utqiagvik (Barrow), Alaska on 28 March 2019. Snow and ice appear as darker shades of cyan in the RGB image, with open water exhibiting a dark blue to black appearance.

A sequence of True Color RGB images from NOAA-20 / Suomi NPP VIIRS and Terra MODIS (below) showed the ice lead becoming wider with time during a 5-hour period (note: the time stamps on the images do not reflect the actual time each satellite passed over the Utqiagvik area). The MODIS image appeared the sharpest, since that instrument has a 250-meter resolution in the visible spectral bands (compared to 375 meters for VIIRS).

True Color RGB images from NOAA-20 and Suomi NPP VIIRS and Terra MODIS [click to play animation]

True Color RGB images from NOAA-20 / Suomi NPP VIIRS and Terra MODIS [click to play animation]

In a 14-day series of Terra MODIS composites (below) it can be seen that the same general ice fracture line had opened and closed a few times during the 15-28 March period, depending on the influences of surface wind stress and sea currents. Days with strong and persistent southwesterly winds led to an opening of the ice lead (such as 20 March); however, the largest 1-day change — and the largest opening of the ice lead — occurred from 27-28 March (MODIS | VIIRS), when the strong southwest winds were bringing unseasonably warm air (over 30ºF above normal) across the area. The daily high temperature at Utqiagvik on 28 March was 30ºF, which set a new record high for the date (the normal high temperature for 28 March is -3ºF). Incidentally, this period of above-normal temperatures contributed to Utqiagvik having its warmest March on record.

Daily composites of Terra MODIS True Color RGB images, 15-28 March [click to play animation]

Daily composites of Terra MODIS True Color RGB images, 15-28 March [click to play animation | MP4]